Touch recognition interfaces have been widely used in home appliances such as mobile phones, smart phones, notebooks, smart TVs, smart refrigerators, audio devices, and the like. Touch recognition interfaces typically use a method of sensing static electricity, sound wave, vibration, and the like to perform a particular instruction. For example, a technology for a touch recognition interface according to the related art has been disclosed in Korean Patent Publication No. 10-0856919.
However, it is difficult for the touch recognition interface technologies according to the related art to support a blind control which enables a user to identify a portion of a touch pad only by tactile sensation, without directly confirming the identified portion with the naked eye. Therefore, when surface roughness of the touch pad is not noticeably different, the user needs to directly identify the portion at which the user's finger is located with the naked eye in order to confirm at which portion of the touch pad a user's finger is located, which causes an inconvenience when in use.
Further, a sound wave recognition-based interface needs to generate a sound wave, and therefore requires a strong touch. However, since an impact when touching the touch pad surface is already transferred to a user's finger or joint, the sound wave recognition based interface may give the user pain. In addition, considering the characteristics of the touch pad, the user may not feel a certain physical feedback, such as being pressed or turned-on in the case of a button, and therefore touch sensation can be insufficient. That is, it may be difficult for the user to recognize whether he/she accurately inputs instructions.